Narrator: HBO's new miniseries, "Chernobyl," recounts the 1986 nuclear disaster in Ukraine. It's a dramatization, so while many events depicted in the show are based in reality, it had a few discrepancies with historical accounts.

Here are 12 of them.

See that thick pillar of black smoke that's coming out of the power plant? It makes for an ominous shot, but in reality, it was more likely thin trails of white vapor that were escaping from the reactor.

In episode one, "Game of Thrones" fans might have recognized Donald Sumpter, the actor who played Maester Luwin. It turns out that his character in "Chernobyl," an elderly Bolshevik by the name of Zharkov, is fictional. His speech urging officials not to raise alarm about the accident, that's also a fabrication.

Zharkov: No one leaves. And cut the phone lines. Contain the spread of misinformation.

Narrator: That doesn't mean there wasn't some effort to contain the spread of information in the immediate aftermath of the meltdown. But we don't know if what Zharkov says here accurately reflects the government's rationale at this point in time.

Chernobyl is the biggest nuclear accident to date, but according to Jan Haverkamp, a senior nuclear-energy expert at Greenpeace, Legasov's comparison of Chernobyl to Hiroshima doesn't quite make sense.

Legasov: The fire we're watching with our own eyes is giving off nearly twice the radiation released by the bomb in Hiroshima.

Narrator: The bomb dropped on Hiroshima was so devastating because of the number of people that suffered direct exposure to radiation. At Chernobyl, on the other hand, radioactive material enters the atmosphere and disperses, so its health effects were more indirect and long-term.

In episode two, a helicopter crashes as it flies over the open reactor. There was a helicopter crash in the wake of Chernobyl, but the show moved this event up chronologically. The crash actually took place in October of that year, months after they were done fighting the fire.

Of the fictional characters in the show, the most central is Ulana Khomyuk, the scientist from the Belarusian Institute for Nuclear Energy. Khomyuk travels to Chernobyl uninvited, interrogates the plant supervisors in their hospital rooms, and soon enough even finds herself in the presence of General Secretary Gorbachev. If that storyline seems unrealistic for one person, it's because Khomyuk was imagined as a composite character to represent the many scientists who led the cleanup effort. Her gender is definitely realistic as the USSR had an impressive record of training women for STEM roles.

In episode two, Khomyuk warns the council that a second explosion could occur, ejecting even more radioactive material from the core at a force of up to 4 megatons. According to Haverkamp, that estimate is probably an exaggeration. The rest of her description doesn't quite hold up either.

Khomyuk: And likely be fatal to the entire population of Kiev, as well as a portion of Minsk. And will impact all of Soviet Ukraine, Latvia, Lithuania, Belarusia, as well as Poland, Czechoslovakia, Hungary, Romania, and most of east Germany.

Narrator: The assertion that all of Europe would be affected involves a lot of hypotheticals. As Haverkamp says, that situation might play out if all of the melting corium hit groundwater. But when corium starts melting, it does so in a very uneven way. So if the second explosion had actually occurred, it'd be pretty difficult to predict the fallout.

As part of the effort to prevent the steam explosion that Khomyuk warned about, three patriotic volunteers dive into radioactive water to open the tank valves. The show takes a few liberties here. According to one of the divers, Alexei Ananenko, they didn't all volunteer for the job. Ananenko was an engineer at the plant who simply happened to be on duty that day when his supervisor assigned him to the mission. He was told he could refuse the assignment, but he was the only person on the shift who knew the location of the valves, leaving him with effectively no choice but to join the team of divers.

In one of the series' more comical moments, the miners digging the tunnel underneath Unit 3 strip naked to cope with the heat. It's possible that a few of the miners actually did this, but even the show's writer and creator, Craig Mazin, said that there were some varying accounts of how much clothing got taken off.

One of the sources that Mazin consulted was "Midnight in Chernobyl," a book based on real accounts of the accident compiled by journalist Adam Higginbotham. In an interview with Inverse, Higginbotham said the show exaggerated the denial and delayed response of the Soviet government.

His book describes how the investigation into Chernobyl began almost immediately on several fronts. Within 36 hours of the explosion, reactor specialists traveled to Chernobyl from Moscow and were able to promptly identify the most likely cause of the accident. Therefore, as Higginbotham said, there was no need for a crusading whistleblower to uncover the causes. But raising awareness about the problems that led to Chernobyl did take Soviet scientists several years of hard work and research.

Sadly, the friendship we see develop between Boris Shcherbina, chairman of the Chernobyl commission, and Valery Legasov, the chief scientific investigator, was largely an imagined one. The duo's scenes together show their growing bond, but there's no evidence that any of these scenes actually happened.

Legasov was also not quite the martyr figure that Jared Harris depicts, raising his voice to Gorbachev and openly challenging the head of the KGB. We have no reason to think that the trial of Dyatlov and the other two plant managers involved any of the theatrics seen in the finale, when Legasov denounces his government in front of a room of officials.

Legasov did die by suicide two years after the explosion, and he did dictate a final letter reflecting on the liquidation effort he spearheaded. But in this message, he didn't ask, "What is the cost of lies," the show's tagline, nor did he contemplate any abstract questions about the meaning of truth.

Legasov: The real danger is that if we hear enough lies then we no longer recognize the truth at all.

Narrator: Legasov did have concrete grievances about the handling of Chernobyl, which he outlined in great detail in his message.